tdf#97700 - vcl: opengl - add asserts for horrible size mismatch.

We really need to be sure that our texture and its wrapper agree on
the size of the texture, and particularly the buffer it is reading
into to avoid DMA'ing junk over the heap.

Add paranoid assertions, also add a canary at the end of the texture
so we fail hard and fast in this case.

Change-Id: Ibf4869fb5cba562aa117943ce0f2f3df21ca7036

1 files changed, 26 insertions, 1 deletions

diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index 2c3ef263678d..be5f8f0d2767 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -38,6 +38,10 @@
 
 #include "opengl/FixedTextureAtlas.hxx"
 
+#if OSL_DEBUG_LEVEL > 0
+#  define CANARY "tex-canary"
+#endif
+
 namespace
 {
 
@@ -147,6 +151,9 @@ bool OpenGLSalBitmap::Create( const OpenGLTexture& rTex, long nX, long nY, long
     mbDirtyTexture = false;
     VCL_GL_INFO( "Created texture " << maTexture.Id() );
 
+    assert(mnWidth == maTexture.GetWidth() &&
+           mnHeight == maTexture.GetHeight());
+
     return true;
 }
 
@@ -258,7 +265,15 @@ bool OpenGLSalBitmap::AllocateUserData()
     {
         try
         {
-            mpUserBuffer = o3tl::make_shared_array<sal_uInt8>(static_cast<sal_uInt32>(mnBytesPerRow) * mnHeight);
+            size_t nToAllocate = static_cast<sal_uInt32>(mnBytesPerRow) * mnHeight;
+#if OSL_DEBUG_LEVEL > 0
+            nToAllocate += sizeof(CANARY);
+#endif
+            mpUserBuffer = o3tl::make_shared_array<sal_uInt8>(nToAllocate);
+#if OSL_DEBUG_LEVEL > 0
+            memcpy(mpUserBuffer.get() + nToAllocate - sizeof(CANARY),
+                   CANARY, sizeof(CANARY));
+#endif
             alloc = true;
         }
         catch (const std::bad_alloc &) {}
@@ -538,9 +553,19 @@ bool OpenGLSalBitmap::ReadTexture()
         // help valgrind & drmemory rescue us - touch last and first bits.
         pData[0] = 0;
         pData[mnBits/8*mnWidth*mnHeight-1] = 0;
+        // if this fails we can read too much into pData
+        assert(mnWidth == maTexture.GetWidth() &&
+               mnHeight == maTexture.GetHeight());
 #endif
 
         maTexture.Read(nFormat, nType, pData);
+
+#if OSL_DEBUG_LEVEL > 0
+        // If we read over the end of pData we have a real hidden memory
+        // corruption problem !
+        size_t nCanary = static_cast<sal_uInt32>(mnBytesPerRow) * mnHeight;
+        assert(!memcmp(pData + nCanary, CANARY, sizeof (CANARY)));
+#endif
         mnBufWidth = mnWidth;
         mnBufHeight = mnHeight;
         return true;